#include <stdio.h>


long long factorial(long long n)
{
    if(n == 0)
        return 1;

    return n * factorial(n - 1);
}

long long comb(long long n, long long r)
{
    long long v1 = factorial(n);
    long long v2 = factorial(r) * factorial(n - r);

    return v1/v2;
}

int main(void)
{
    long long sum = 0;
    const long long magnitude = 27;
    for(long long i = 0; i < magnitude; i ++)
    {
        sum += comb(magnitude, i);
    }

    printf("%lld\n", sum);
    return 0;
}
